1. Field of the Invention
The present invention relates to an inlet system which supplies intake air to an engine.
2. Description of Related Art
Conventionally, in an inlet system, a part of exhaust gas from an internal combustion engine is mixed with fresh air to be suctioned into a cylinder, in order to reduce nitrogen oxide in exhaust gas or to improve fuel mileage at the time of partial loading. (The exhaust gas mixed with fresh air in the inlet system is hereinafter referred to as EGR (exhaust gas recirculation) gas).
EGR gas blows off into the inside of an intake manifold, and is mixed with fresh air in the intake manifold to be suctioned into each cylinder. Accordingly, it is necessary to arrange the gas outlet of EGR gas at a predetermined target position in order that EGR gas may be suctioned evenly into each cylinder (see e.g., JP7-189643A).
However, in order to arrange the gas outlet (leading end of an EGR inlet) of EGR gas at the target position, it is necessary to make a leading end of the EGR inlet project to the target position, changing a position of the EGR inlet in various manners. Accordingly, the EGR inlet is extremely troublesomely attached to the intake manifold, which is one of factors in cost rising of the inlet system.
In order to improve the workability in attaching the EGR inlet, the complicatedness of changing the position of the EGR inlet in attaching the EGR inlet may be mitigated by expanding an opening diameter of an insertion portion into the inside of the intake manifold. However, since rigidity of the intake manifold becomes lower as the opening diameter of the insertion portion becomes larger, the method of simply enlarging the opening diameter is not desirable.